Apparatus for accelerating charged particles



April l, 1958 H. R. KRA-rz 2,829,249

APPARATUS Fon AccELERATING CHARGED PARTICLES Filed Aug. 21. 1952 :ssheets-sheet 1 l Inventor:

Howard R. Kvatz, 2 b5 His .tctowvxey` April 1, 1958 H. R. KRATz2,829,249

APPARATUS FOR ACCELERATING CHARGED PARTIcLEs Filed Aug. 21, 1952 f i ssheets-smet 2 "Env l 0075/? WM/@wss Flg. E? I l x x fk f 0 (l TERWIND/NGS wenas/M; r Y y www wmp/mas ITV GTTCCDP: Z Howard R. Kratz,

by. A His Attorneg.

Apil 1, 1958 H. R. KRA-rz 2,829,249

APPARATUS Fox ACCEL'ERATING HARGEn PAR'ncLEs Filed Aug. 21, 1952 3Sheets-Sheet 3 rig. 44.

8574590 SBII 008/7' Pf6/0N P ra mamme o la 4r ans/fa Par/l Inventor* tHoward R. Kratz 'United States Patent() PPRATUS FOR ACCELERATING CHARGEDPARTICLES Howard R. Kratz, Schenectady, N. Y., assignor to GeneralElectric Company, a corporation of New York Application August 21, 1952,Serial No. 305,613

9 Claims. (Cl. Z50-27) The present invention relates to apparatus forimparting high energy to charged particles, particularly electrons..This invention relates particularly to and is an improvement overapparatus of the type disclosed in Patent 2,622,194, granted December16, 1952, upony an application of James L. Lawson, Howard R. Kratz andGeorge L. Ragan, Serial No. 196,482, filed November 18, 1950, andassigned to the assignee of the present application.

Itis now well known that energy of the order of several million electronvolts or higher may be imparted to charged particles such as electronsby accelerating the particles in a generally circular path or orbit withmagnetic induction effects. For example, apparatus for producing thisresult is disclosed inV U. S. Patent 2,394,071, granted February 5,1946, to Willem F. Westendorp and assigned to the assignee of thepresent invention. Such apparatus yis commonly referred to in the art asa betatron, and itcomprises field generating means for providing atime-varying magnetic flux which links the orbital path to acceleratethe particles and a time-varying magnetic guide field which traversesthe locus of the orbital path for constraining they particles thereto.

It is also known that further energy may be imparted to chargedparticles such as electrons by subjecting them to the repetitive actionof a localized cyclically-varyingv electric field after they have beenaccelerated to a desired energy level by the above-mentioned betatronapparatus. Suitable apparatus for achieving this purpose is disclosed inU. S. Patent 2,485,409, granted October 18, 1949, to Herbert C. Pollockand Willem F. Westendorp and also assigned to the assignee of thisinvention. This latter apparatus can be referred to as synchrotronapparatus utilizing betatron start. It generally comprises means such asa high frequency resonator coupled to the charged particle orbital pathfor applying a localized cyclicallyvarying electric field to acceleratethe particles after they have been pre-accelerated by betatron action,and means for producing a time-varying magnetic guide field traversingthe locus of the orbital path for constraining the particles theretoduring the application of the electric field.

Both of the forms of accelerator apparatus disclosed in theabove-mentioned patents employ Yanl iron core for the production of theproper magnetic fields andy fiuxes. cause such an iron core must belaminated'to minimize the generation of eddy currents and has greatweight, fabrication and handling present major problems. vMoreover, itis very difficult to eliminate azimuthal field asymmetries, and thelimitations upon magnetic inductionimposed by saturation of the ironnecessitate large amounts of stored energy in the accelerator apparatus.The aforementioned Lawson et al. Patent 2,622,194 showsthatthedisadvantages represented by theiron core may be obviated by theexpedient of producing the desired magnetic fields and fluxes withnon-ferromagnetic field generating means. f Y

In the aforementioned Patent 2,622,194 there Vvis disclosednon-ferromagnetic .charged particle accelerating 'apparatus whichcomprises non-ferromagnetic field generating means enclosed by a metaltank adapted for internal evacuation. Within the metal tank is disposeda nonferromagnetic liner which has the same general shape as the tankand also encloses the field generating means.

The field generating means includes two sets of windings,

one of which provides the requisite time-Varying magnetic liux and guidefield for initially applying betatron acceleration to charged particlessuitably introduced into the tank, and the other of which provides thetime-varying magnetic guide field which is required during thesubsequent period of synchrotron acceleration. This construction allowsthe placement of the synchrotron guide field windings in a regionclosely adjacent the stable orbitaly satisfactory, it has been foundthat the set of betatron As shown and described in the aforesaid patent,the set lof windings expends morey power than is desirable.

betatron windings comprises four individual coils or windings suitablycoupled with the charged particle orbital p'ath to produce the betatronfield and flux. For obtaining a stable region surrounding the orbitalpathY of suiiciently great cross-sectional area to permit fullysuccessful acceleration of charged particles, it has been foundnecessary to locate the individual betatron windings farther from theorbital path than was anticipated. This has two undesirable effects: (l)the coupling to the orbital path s less, thus reducing the efficiency ofthe windings; and (2) the windings, being nearer the non-ferromagneticliner,

cause more power to be wastefully dissipated in the liner by currentsgenerated therein. j

It is a principal object of the present invention to provide a means forreducing the power Yconsumption of nonferromagnetic betatron field andux generating windings.

' f According to one aspect of the present invention, there is providedimproved non-ferromagnetic charged particle yaccelerating apparatuswhich comprises four betatron windings for a given extent of the stableregion of acceleration surrounding the orbital path, there is providedan auxiliary winding located in the plane of the orbital path. Theauxiliary winding is energized such that it carries a current fiowing ina predetermined direction with respect to the current in the remainingfour betatron field and flux generating windings, whereby the net fieldof the four Abetatron windings is modified ina manner which' permitstheir location more closely adjacent `the' orbitalv path for a givendesired extent of the stable orbital region. Following initialacceleration of the charged particles with the five-winding geometry ofthe invention, synchrotron acceleration of the charged particles tohigher energy'.Y

levels can be accomplished, if desired, by the provision'of synchrotronguide field windings and a cyclically-varyingelectric field coupled tothe electric path.

Other objects and advantages of this invention willbe apparent from thefollowing description taken in ,connection with'the accompanyingdrawings in which Fig.` 1 is a sectionalized elevation ofnon-ferromagneticsynchrotron apparatus suitablyembodying the inventionand taken along line 1-1 ofk Fig. 2; Fig. 2 isa sectionalized viewPatented Apr. 1, 1958 graphical representations useful in explaining theinvention; Fig. is a schematic diagram showing exemplary circuitconnections for energizing the apparatus of Figs. 1 and 2;.and Fig. 6 isanother graphical representation useful` in explaining the invention.`

Referring now to Figs. l and 2, there is shown nonferromagnetic chargedparticle. accelerating apparatus according to the invention comprisingan air-tight tank 1 which may` befevacuated, through a `suitableconnection 2 attached `to the baseplate `3 of tank 1. Base plate 3 and acover plate 4 may be retained in air-tight relation with respect to acylinder. 5 by means of a plurality of peripherally spaced screwsinserted through circular gaskets 7, which may consist of a suitablesynthetic rubber material. Basle` plate, cover plate 4, and cylinder 5,which dene chamber 5', must beA of `sufficient thickness to withstandinternal evacuation without` serious deformation and, therefore, shouldconsist of a high tensile strength materiaLsuchas steel or iron. p

. Supported from base plate 3 by means of circular dielectricmspacer`members 8 and 9 is a liner l0, the function of which will be more fullyvdescribed hereinafter. Liner 10 preferably consists of a highly,conductive non-ferromagnetic material `such as copper and comprises abase plate 11,'a, cover plate 12 and a hollow cylinder 13. Base plate 11and cover plate12rare attached to cylinder 13 by means of alplurality of peripherally spaced screws 14, and

an`orit`1ce-15 is provided in base plate 11 to permit inter-- nalevacuation of` liner 10 through connection 2. For the sake.- of`symmetry,an orifice 15' is situated in cover- Plate 12..

`In order'to` provide for the injection of charged particles suchaselectronstfor accelerationwithin liner 10, there is, showna` sourceassembly 16 which may comprise an electron gun 17 `having altilamentarycathode (not shown) suitable for injecting, in responseto intermittentenergiza-A tion, aburst of electrons` into` the charged particleorbital.

path indicated at;` point x. Structural details for gun 17, whicbrmaybe`advantageously employed in connection with thepresent invention, aredisclosed and claimed in U. S. Patent 2,499,192,` granted February 28,1950, to James M. Lafferty and assigned to the assignee of the presentinvention.w Guni17 maybe supported within a hollow tubel ofahw-conductivity, non-ferromagnetic t materialrsuch` as .stainless steelandenergized through conductors. (not shown) insulatingly introducedthrough tubel. y A slot lisprovidedin the lower end of tube 18to permittheegressof electrons from gun 17. Tube 18x is ared outwardly at itsupper end to receive in' hermetierclationship an insulator 19 and isalso hermetically sealed adjacent its upper end to a base member 20.

An apertured. plate 214 Ais helduY bymeans.. of screws 22` gun 17 ismaintained by meansof a stud 29 and-nuts 3G,v

thelattenof which may-tbe" screwed `up or down to adjust bellows 25.ASeveralstuds 29,' along with nuts 30, may

beflocated `around the periphery of `base member to insure desiredpositioning of gun'17.'

Aslhasbeen mentioned heretofore, the present inventin; contemplates theY betatron acceleration` Aof injected charged particles withnon-ferromagnetic field` generatingr means capable of supplying both atime-varying magnetic flux ywhich linksthe orbital path of the chargedparticles* to impart acceleration theretoy andga time-varying magneticlguide teldwhich traverses the-orbital pathfor` the` purpose `ofconstraining the charged particles thereto. Ac-

cordingly, beta'tron windingsl, 32,133Jand-34 are-shown' potliti'oned`adiacentithe orbital'ipath `indicated at point x;-

of voltage (not shown) such that the current through all the windingsows in the same direction for a purpose to be more fully describedhereinafter. Conductors 36 are hermetically sealed within tank 1 bymeans of insulators 37, apertured plates 38, screws 39v and packingmaterial 40. To prevent a conductive connection to liner 10, conductors36 are inserted therein through apertures 41. Windings 31, 32', 33 and34 are respectively supported from base plate 11 of liner 10 by means ofdielectric spacers 42, coil supports 43, 44, 45 and 45,cylindricallyshaped spacer members 47 and-48 and dielectric shimmingmembers 49, 50," 51 and 52.

To assure the retention of `proper positioning of field generatingwindingsl, 32, 33 and 34, as well as of other components of theaccelerating apparatus, during operational periods when tremendousforces are exerted thereupon due to the magnetic fields and fluxes whichare generated, various support members are provided. These membersinclude dielectric spokes 53fwhich bear attheir outer` ends againstangedhollow cylindrical members 55. Outward radial thrust may be imparted tospokes 53 by means of spreaders 56. Spreaders 56 comprise lower beveledcylindricalldielectric blocks 57 having studs 58 extending therefrom.Upper dielectric cylindrical beveled blocks 59 are apertured to permitthe extension therethrough of studs 58 and block members 57 and 59 maybe drawn together to exert outward radial thrust against cylindricalmembers 55. by means of dielectric nuts 60 which threadably engage stud58. Notched circular dielectric spacer 61. is provided, as shown, toassure proper separation of members 47 and 48. To exert radial thrustbetween cylinder 13 of liner 10 and flanged cylindrical members 62,cylindrical spacer members 63 and 64 are employed in'connection withspreader members 65, which are similar to the above described spreadermembers 56 l and compriseupperand lower blocks 66 and 67, studs 68, andnuts 69. Y i

The Ndielectric `materials-utilized to form the various above-mentionedYsupports -must be able to withstand the tremendous-forcestwhichareexertedltherreupon when the accelerating apparatusis `in operation;Furthermore, the

" by winding glass cloth,which has been impregnated with a suitableorganic resin,4 around a steel mandrel having a desired shape. Afterthedesired form has been obtained in this manner, the support may be curedand stripped from the mandrel in amanner well known to those skilled inthe. art. Subsequently, the supportmay be machined tothedesirecldimensions. A suitable organic resin may consist of.-diallyl phthalateanddiethylene glycol maleate alongwith a` polyvinyl. formal resinobtained by the partial .hydrolysisolf polyvinyl acetate and thereaction ofjhefpartially hydrolized` product with formaldehyde.

It willnow appear. that, if the betatron field and flux producingwindings.31--34areenergized from a source of time-varying. voltagein. amanner to be more fully dscribedher'einaftemacceleration in-an orbitalPahf charged. particleslinjected fromv gun 17. may be obtained,providingtthb ,well known betatron flux and iield consider ations `aresatised.` Thebetatron relationships which` they time atrwhichthemagnetic induction' B' is aero, ro

. (1 where'lnpisthe total changein tlux linking the orbit from agsaaatnis the radius of the o'rbit, and Bo is the magnetic vinduction at theorbit; and

where n is an exponent having a value between O and 1, B is the magneticinduction at a position under consideration and r is the radius of sucha position. Equation 1 represents the ux-field condition which must becomplied with to secure successful acceleration, and Equation 2represents a stability condition which must be fulfilled before thecharged particles will execute stable oscillations along and in thevicinity of the orbital path. In

order to satisfy Equation 1, which need be met only along the stableorbit x, with two windings outside and two winding inside stable orbit xas shown, it is necessary to have the current liowing in all thewindings in the same direction, whereupon the flux linking the orbitalpath is then in the same direction from both inner and outer windingswhile the field traversing the orbital path from the inner windings isopposite that from the outer windings. With the proper ratio of thenumber of turns in the outer windings to the number of turns in theinner winding, Equation 1 can be fulfilled. Equation 2 requires anearly'uniform field which falls off in proportion to l/rn in the regionalong and adjacent orbital path x. In order to fulfill Equation 2, it isnecessary to match the shape of the magnetic induction curves of innerwindings 31, 34 and outer windings 32, 33 such that the net magneticinduction falls off at the proper rate with the radius in the orbitalregion. In Fig. 3, curves of magnetic induction B in the orbital planeversus radiusV r are shown for both inner windings 31 and 34 and outerwindings 32 and 33. It will be observed from Fig. 3 that the desiredfalling off of magnetic induction with radius to give a value of n lyingbetween and 1 can be obtained at or near the field maxima of both innerand outer windings. This is more clearly shown in Figs. 3a which can beconsidered as an enlarged View of the righthand portion of Fig. 3.

It has been found in practice, however, that the proper positioning ofwindings 31-34, to secure a stable region surrounding the orbital pathin accordance with Equation 2 of sufiicient extent to permit fullysuccessful acceleration of the charged particles, requires the locationof, these windings at relatively great distances from the orbital path.This reduces the coupling to the orbital path and hence reduces theefficiency of windings 31-34.`

And since it is desirable to keep the dimensions of liner l@ as small aspossible to reduce the volume which must be evacuated, the positioningof windings farther from the orbital path places them nearer liner 10,thereby iucreasing wasteful power dissipation from eddy or imagecurrents generated in the liner as la result of the timevaryin.'Jcurrents flowing in the windings. y

When the net magnetic induction of vthe windings StL-34 is plotted as afunction of radius for various planes above and below the plane of theorbit, it is observed that the exponentvn, which is proportional to theabsolute magnitude of the slope of the magnetic induction versus radiuscurves, decreases in moving vertically (or in the Z direction parallelto the axis of the windings) from the orbital plane. It is this decreasein n that limits the vertical or Z direction extent of the stableorbital region. As the windings 31-34 are placed nearer the orbit, ndecreases more rapidly and the stable region surrounding the orbitbecomes smaller. According to the invention, this decrease in n in thevertical or Z direction is made less rapid by positioning an auxiliarywinding 69 in the plane of the orbital path as illustrated;

in Figs. 1 Yand 2. Winding 69 has a radius smaller than that of theorbit andis connected, as will be more fully described` hereinafter, inseries with windings 31-34 so that itlcarries a current flowing in the same direction as the currentrin windings 31-34. VAlthough Winding 69' isshown as comprising only one turn, it can have addi`i tional turnsdepending upon the number of ampere-turns that are necessary to producethe desired compensation for the decrease in the n of the windings31--34.

The magnetic induction yof winding 69 alone, plottedA netic induction ofwindings 31-34 in the orbital plane;

hence the n value of net magnetic induction of the entire combination ofwindings 31--34 and 69 decreases more t slowly with Z than does themagnetic induction of windings 31--34 alone. This is readily understoodfrom the fact that the magnetic induction of winding 69 decreases the nvalue of the net magnetic induction of windings 31-34 more in theorbital plane than above or below it. Since the n'value of the entirecombination of windings 31--34 and 69 decreases more slowly with Z, itthus becornes possible to locate windings 31-34 nearer the orbit withoutdecreasing the extent of the stable orbital region in the vertical or Zdirection.

s, The utilization of auxiliary winding 69 also affects# the n value ofwindings 31-34 in the radial direction.

The magnetic induction of winding 69 decreases the` value of n in theorbital plane, but thisV effect is more pronounced at radii smaller thanthe orbit since the n value of the magnetic induction of winding 69(which subtracts from the n of windingsv31-34) increases asy the windingitself is approached. As the winding 69 -is approached from the orbit,the n value for the entirecombination of windings 31-34, 69 actuallydecreases Y' to zero and becomes negative. The radius atpwhich n becomeszero is determined by the radius of winding 69' and the magnitude of themagnetic induction from wind` ing 69' as compared withV the magneticinduction from windings B11- 34. By a proper choice of the radius andnumber of turns of winding 69', the extent of the stable region can beextended to smaller radii without much affecting the radius outside theorbit at which the field becomes unstable. 69' can increase the totalextent of the stable region in the radial direction as well as in thevertical or Z` Of course, the magnitude of the magnetic direction.induction which can be supplied from winding 69 yis ultimately limitedby its effect upon the magnetic induction outside the orbit.

Although it is preferred to position winding 69 in the plane of theorbital path and with a radius smaller than the path, it can also beemployed in the plane of the orbit with a radius larger than the path.In such event,v

the energization of winding 69' can be by a series connection withwindings 31-34, but the current in winding 69' must flow in a directionopposite to that in wind-v l ings 251-34.

in the inner section must be in the same direction as the current inwindings 31--34 and the current flow inthe outer section must be in theopposite direction.

While it is known that the above-stated Equations 1 and 2 both must befulfilled to obtain betatron acceleration of the charged particles, ithas proved impractical to` I calculate accurately the fieldconfigurations resulting fromv windings 31-34 and 69' because of thedifficulty of con-4 sidering the effect of liner 10. Liner 10 isemployed,.

in conjunction with tank 1, as a shield for the field generatingwindings and `for external apparatus. YLiner 10,. however, reducesvthefield at the orbit and the flux linking` the orbit'and alsov changes thephases'of the field 4and' 'flux In this' way the addition of windingwith respectto the current in windings 31--34, 69'.` Consequently, themost effective procedure for locating` whichsatises Equatioirl alongorbital path x and` also` produces a satisfactory `field `variation in`bothlsadial and vertical directions over the desired stable' region inlthe vicinity of the orbital path as `required by Equation 2. Afterwindings 31m-34,` 69' have been installed within liner 10, vertical`adjustment to correct for field discrep ancies may be obtained :byImeans of shirns49--52. With the above-described winding .configurationa stable region of relatively large extent adjacent the orbital path`can be obtained, the shape `of suchfa `region `being indicated by thesolid `line representation of Fig, 4.

After'thechargedparticles have been accelerated to the desired energylevel byrneans of betatron flux and field producing windings 31-34 and69", further energy can be imparted to the particles by means of acyclicallyvarying `electric field produced by a high frequency circuitincluding a resonator 7 0i Resonator 70 isof the opencircuited coaxialline type in which a portion of an electrostatic shield 71, whosegeneral functions will be more fullydescribed hereinafter, serves as the`outer conductor and a lplurality of vertical conductors 72 serve as theinner conductor. Both electrostaticshield 71 and inner conductors 72are`constructed of a plurality of separate wires of a non-ferromagneticconductive material such as copper depending from cover `plate .12 ofliner 10 as shown, the individual wires being` secured together by meansof a desired `insulating organic resin, such as the abovementioneddiallyl phthalate and diethylene glycol maleate.

This form of construction serves to minimize the generation ofdisturbing eddy Lcurrentsgwhen the accelerating apparatus is'inoperation. Withinconductors 72 a similar pluralitycf conductors 73 areprovided, which, along with conductors `72, may subtend an arc of about60 adjacent orbital path x. Conductors 72tand 73 areV bent outward attheir upper ends and soldered at 74 to a circular lplate 75 of anou-ferromagnetic conductive material such Ias copper which is secured,along with shield 71, to `cover plate 12 by means of right angle'circular clamping members 76 and bolts 77 constructed from anon-ferromagnetic conductive material such as copper. Arcuate dielectricmember 78 is positioned within conductors 73 `to provide rigidity fortheyconductor assembly comprising conductors 72 and 73. Each ofthe;wires of`shield71` and each of the conductors 72 Aand 73 may beprovided, respectively, with circumferential slots 79, 80 and 81 `tointerrupt continuous current'paths for unwanted eddy currents.

It will `now be observed that, if resonator 70 is excited with anenergized concentric line `i12 hermetically introduced through coverplate 4 by means of a vacuum-tight bushing 83 and inductively coupledinto resonator 70 at 84, a cyclically-varying electric field will beproduced between outer conductor 71 and inner` conductor 72, such afield fringing out atthe ends of resonator 70 tocouple with the orbitalpath x. lf this electric field is of the proper frequency, energy may beimparted to charged particles during each revolution within orbital pathx. Assuming that the `charged particles are electrons and have beenaccelerated to approximately the velocity of light within orbital path xby betatron flux and field generating `windings 31-34, their approximate:frequency j" will be given `by the followingrelation:

where `c lrepresents thevelocity of light. Consequently, thejfrequencyof excitation of resonatorf70 maybe arranged at a constant value suchthat energy is imparted to the charged particles upon each revolution.

According to the present invention, conductors 72 areprovided withextensions extending downwardly and about the charged particle orbitalpath x while conductors 73 terminate vertical extension, above the pathas indicated. This Yprovides an R. F. field-free region 85 throughout.the vcircumferential extension of conductors 72 and 73, `suchfield-free region serving to shield the .charged `particles ,from the`R. E, fields within resonator n, while they are within region S5'.Therefore, if the frequency of excitation of resonator 7i) is equal toor a multiple of `the frequency given a Equation 3 for electrons, energymay be imparted` to the electrons a function ofthe timeatwhich theyenter and leave resonator 7G.

Of course, charged particles moving along orbital path x are affected byany electric held which couples thereto. In order to prevent deleteriousresults, therefore, it is necessary to shield the orbital path fromunwanted electric fields, e. g. those resulting from the clcctricpotentials upon `the various windings within the accelerator apparatusand those derived from charges collecting upon partsof the apparatus`(especially insulators). Elec trostatic shield 71, describedhereinbefore, acts to perform this function. Shield 71 may beconstructed of hollow wires and water-cooledit excessive overheating isencountered. Slots 79, as well as slots 39 and 81, may not be necessary,providing the respective conductors lie within close limits in planespassing through the axis of the accelerator apparatus.

In order to provide a time-varying magnetic guide field to constrain thecharged particles to orbital path x as energy is being imparted theretoby resonator '70 in accordance with the .principles hercinbcforediscussed, windings 86,87, S8 and G9 are disposed adjacent orbital pathxdwithin circumferential slots in cylindrical spacer members 47 and 48as shown. windings i3d-89 may comprise a plurality of tubes throughwhich a suitable coolant such aswater may be circulated and to whichenergy may be supplied through hermetically sealed conductors (notshown) introduced through tank 1 in a manner similar' to conductors 36.The magnetic field provided by windings 36-39 must meet the requirementsof Equation l2 in that the magnetic guide field within the regionsurrounding orbit x must have the desired inverse slope with increasingradius; but the flux generated by windings 86-89 need not meet therequirements of Equation 1 since, Vduring the period of energization ofwindings 86-89, energy is imparted to the charged particles by means ofresonator 70 and not by means of a time-varying magnetic flux linkingthe orbit, as is the case during betatron acceleration. To produce afield complying with Equation 2 alone, a more efcient field producingarrangement may be employed, viz. windings 86-89 may be connected inseries to a suitable source of time-varying voltage (not shown) suchthat the current in the two inner windings 86 and 89 flows in theopposite direction to the current flowing in the two outer windings 87and 83, the direction vof current flow in the outer windings being thesame as the current flow in betatron windings 31-34 and 69. This resultsin a greater guide field intensity for a given winding current becausethe fields are 4additive within the stable orbit region. The value ofthe exponent n in Equation 2 in this instance depends upon the relativevertical spacings of the outer windings 87 and S8 compared to therelative vertical spacings of the inner windings 86 and 89, and thedesired value may be obtained with the outer windings slightly fartherapart vertically than the inner windings. The crossesectional area ofthe orbital stable region will have dependent dimensons, i. e. thevertical extent may be increased by moving the windings farther apartvertically (without altering relative vertical spacings) but thehorizontal extent will be decreased simultaneously and however, theycannot be in too close proximity because, v

matterfthe cross-sectional -A even though the amplitude of the chargedparticle osci1 lations has been damped during the betatron start period,

the charged particles still undergo some oscillation about orbital pathx. Moreover, even though the charged parl ticles are electrons and havebeen accelerated to nearly i the velocity of` light during the betatronstart period,

there is a slight increase in radius vof orbital path x as ar result ofrelatively small velocity increase during chrotron acceleration to highenergylevels.

Referring now to the exemplary circuitry of Figs. 5

syn-

.and 6,4 the following sequenceof events takes place afterv switch 100of Fig. 5 is closed. As will be observed, betatron flux and lieldgenerating windings 31-34 and 69', which may be series resonated withcapacitors 101, are connected to be energized in series by atime-varying alone. If it is found that the region surrounding the"`orbital path can not be evacuated suiiiciently, electrostatic shield 71in conjunction with the cover plate 4 of Y tank 1 can be formed into aseparate hermetically sealed without actually departing from theinvention. I therefore aim in the appended claims to cover all suchequivalent variations as come within the true spirit and scope of theforegoing disclosure.

What I claim as new and desire to secure by Letters 4 Patent of theUnited States is:

source of voltage, such as alternating current source 102 pulse in itssecondary circuit as the current through windings 31-34, 69' and theflux generated thereby goes through zero. In a few microsecondsthereafter when the magnetic induction at the orbital path x has reachedparticles can be accelerated along an orbital path; means for injectingsaid charged particles for acceleration within Asaid chamber; a setofwindings for accelerating said particles along said orbital pathincluding an outer pair of windings having aY diameter greater than saidorbital path, an inner pair of windings having a diameter less than saidorbital path and a winding positioned essentially in the plane of .saidorbital path adjacent and substantially non-coplanar to said inner andouter windings, said windings in said inner Aand outer pairs beingconnected together for current ilow therethrough in the same direction,each winding in each of said inner and outer pairs of windings beingdisposed on the opposite side of the a value which causes chargedparticles of several kilovolts energy to be constrained thereto, such asthe point a of Fig. 6 wherein the net magnetic induction B inthe orbitalplane is plotted versus time, gun 17 is energized by means of pulsegenerator 104, the initiation of which is deter,- mined by delay device105. The charged particles which are thus introducedinto orbital path xare accelerated by the betatron ilux and field generating windings31--34 and 69until they have reached a desired energy level, at` whichtime delay device 106 causes highV frequency. gen.

erator 107 to energize resonator 70. Within close proximity thereto,delay device 108 causes pulse generator 109 to energize synchrotronguide field windings 556-89. This latter sequence may be arranged tooccur at point b as indicated on Fig. 6. After the charged particleshave been accelerated further or desired additional energy has beenimparted thereto by synchrotron guide field windings 86-39 and resonator70, delay device 111 may be rendered effective to deenergize highfrequency generator 107 at point c whereby the charged particles spiralinwardly from orbital path x from impingement upon a suitable target(not shown). Alternatively, delay device 111 can be rendered operativeafter the magnetic induction peak d has been traversed, e. g. the pointe on Fig. 6, whereby the charged particles spiral outwardly and may bedirected to a suitable target 112 (Fig. 2) for the production of desiredeffects. If the charged particles are electrons, high energy X-rays maybe generated in this manner and extracted from tank 1 through acircumferential groove 113 (Fig. l) within cylindrical member 48, a slot113 in shield 71 (Fig. 2), and a port 114 (Fig. 2).

It will be understood by those well skilled inthe art that various formsof delay devices, pulse generators, and high frequency generators may beemployed to secure the above mentioned purposes. It will'also beunderstood that windings 31--34, 69 and capacitors 101 can be energizedin parallel by means of source 102 and transformer 103, although theabove described series connection is to be preferred because harmonicsin supply voltage are ltered and short-circuits in windings 31-34, 69are current-limited. From the foregoing description, it is apparent thatwindings 31-34 and V69 can be advantageously employed without theassociated synchrotron windings and circuitry for the purpose Vofaccelerating charged particles to high energy levels by betatron etectsplaney of said orbital path in relation to the remaining winding of eachrespective pair and all ofV said windings enclosing a space which issubstantially free of ferromagnetic material; and means forsimultaneously energizing all of said windings including a source oftime-varying voltage connected thereto.

2. Apparatus for accelerating Vcharged particles comprising meansproviding a chamber within which charged particles can be acceleratedalong an orbital path; means for injecting said charged particles foracceleration within said chamber; a set of windings for acceleratingsaid particles along said'orbital path including 'an outer pair ofwindings having a diameter greater than said orbital path, an inner pairof windings having a diameter less than said orbital path and a windingpositioned essentially in the plane of said orbital path adjacent saidinner and outer windings, said windings in said inner and outer pairsbeing connected together for current flow therethrough in the samedirection, each winding in each of said inner and outer pairs ofwindings being disposed on the opposite side of the plane of saidorbital path in relation to the remaining winding of each respectivepair and all of said windings enclosing a space which is substantiallyfree of ferromagnetic material; and electric conducting means connectedto and interconnecting all of said windings for simultaneously supplyinga time-varying voltage thereto to produce coincidentally both atime-varying magnetic flux which links said orbital path to acceleratesaid charged particles and a time-varying magnetic guide lield whichtraverses said orbital path to constrain said particles to follow saidorbital path within a relatively large radially and axially extendingstable region surrounding said oroital path.

3. Apparatus as in claim 2 in lwhich said winding positioned essentiallyin the plane of said orbital path has a diameter less than the diameterof said orbital path and is wound and connected relative to theremainder of said y windings so that when energized it carries a currentflow- ,owing in a direction opposite to that flowing Ain the` remainderof said windings.

5. Apparatus as in claim 2 in which said Windinglpositioned essentiallyinthe plane of said orbital Vpath includes two sections, one of saidsections having a diameter greater than that of said orbital path andthe other of said sections having a diameter `less than that of saidorbital path, said one section being wound and connected relative to theremainder of said windings so that when energized it carries a currentowing in a direction opposite to that oiving in the remainder of saidwindings and said other section being wound and connected relative tothe remainder of said windings so that when energized it carries acurrent tiowing in the same direction as that flowing in the remainderof said windings.

6. In non-ferromagnetic accelerating apparatus wherein charged particlesare accelerated along an orbital path by means of a set ofnon-ferromagnetic cored windings connected together for currenttlow inthe same direction to supply a time-varying magnetic ux that links theorbital path to accelerate the charged particles and'a time-varyingmagnetic guide eld that traverses the orbital path to constrain theparticles thereto, the improvement which comprises means for increasingthe stable region within which charged particles `can be acceleratedalong the orbital path including a non-ferromagnetic cored windingpositioned essentiallyv in the plane of the orbital path and Iconnectedfor simultaneous energization with said set of windings to supplymagnetic ux and tield supplementary to the magnetic ux and eld suppliedby the set of windings.

7. In non-ferromagnetic accelerating apparatus wherein charged particlesare accelerated along an orbital path by means ofa set ofnon-ferromagnetic cored windings connected together for current flow inthe same direction to supply a timevarying magnetic flux that links theorbital path to accelerate the charged particles and a time-varyingmagnetic guide field that traverses the orbital path to constrain theparticles thereto, the improvement which comprises means for increasingthe stable region within which charged particles can be acceleratedalong the orbital path including a non-ferromagnetic cored,

winding positioned essentially in the plane of the orbital path andconnected in series with the set of windings to` supply magnetic fluxand iield supplementary to the 5magnetic, ux and held supplied by theyset of windings.

8L ln a non-ferromagnetic synchrotron having a set of betatron windingsconnected together for current ow in the same direction for initiallyaccelerating charged particlesalong an orbital path and electrieeldproducing means for continuing the charged particle acceleration,

the improvement which comprises means for increasing the stable regionwithin which `charged particles can be accelerated along the orbitalpath including a non-ferromagnetic cored winding positioned essentiallyin the plane of the orbital path and connected for simultaneousencrgization with said betatron windings to supply magpath and connectedfor simultaneous energization with` said betatron windings to supplymagnetic ux and iields supplementary to the magnetic flux and fieldssupplied by said betatron windings.

References Cited in the file of `this patent UNITED STATES PATENTS2,465,786 Blewett Mar. 29, 1949 2,473,477 Smith June l4, 1949 2,533,859Wideroe Dec. 12, 1950 2,622,194 Lawson et al. Dec. 16, 1952 2,736,799Christotilos Feb. 28, 1956`

